Madonna's Material boy

The '4 Minutes' singer says her adopted tot David, four, is her biggest fan and is fascinated by the outfits she wears in her pop promos and on stage.

She said: "He knows every song, every word, every step, and he wants to wear all the costumes. He likes my dress that I wear in 'La Isla Bonita'."

Madonna, 51, also revealed her other children are showing signs of following in her footsteps and she was particularly impressed with her eight-year-old son Rocco - whose father is her ex-husband Guy Ritchie - joining her on stage at her 'Sticky and Sweet' world tour because he is usually so introverted.

She added: "When he jumped on stage to dance in my last show I was shocked actually and secretly, unbeknownst to me, they're all studying privately with my dancers.

"Rocco comes out and busts out like a moonwalk or, you know, some kind of break dancing move and I'll ask him, 'Where did you get that?' He's always been quite shy so I was shocked when he wanted to be in the show."

The singer's 13-year-old daughter Lourdes also joined her mother on stage and astonished the 'Celebration' star with her professionalism.

She told 'GMTV': "I really thought of her in a very professional way, and I didn't want to distract her.

"I checked her out a few times in the show and she looked so chilled out and laid back and nonplussed by the whole thing, that I was like, 'OK. I'm not worried about her!' "

Despite her worldwide fame, Madonna - who also has an adopted daughter, Mercy, four - insists the children cope well with the attention surrounding her and them and manage to stay grounded.

She added: "They get great bonuses and perks out of being my children and they know it, and they're very grateful and appreciative for it.

"I think they are pretty balanced in terms of how they view fame or celebrity or things like that. I think it took them a while to adjust, but I think they're OK about it."